This invention relates to thermosetting furan based resins containing niobium and/or tantalum chemically bonded in the backbone of the polymer.
In preparing high-temperature, corrosion and ablative resistant structures, it is the practice to impregnate refractory materials with a synthetic resin, shape the structure to the desired form, and thereafter finally cure the resin at the necessary elevated temperatures. Useful resins used heretofore for this purpose have included, for example, phenolic resins, epoxy resins and the like. With the advent of aerospace products, the requirements for materials having suitable ablative characteristics have become even more critical and, accordingly, the presence of carbonized products has found particular acceptable application in this field. Thus, in preparing such products, resin impregnated refractory materials such as silica, carbon and graphite fibers and fabrics have been heated at high temperatures in order to reduce the impregnated resins substantially to carbon. The resulting products have improved high-temperature characteristics due to the carbonized matrix materials present therein. The properties of the resins used to impregnate and coat the refractory fiber materials must be such that during the pyrolysis outgassing problems are minimized with a substantial amount of the original resin material being retained in the form of carbon matrix in the product structure. Thus, resin products, which upon carbonization undergo extensive volatilization, will not only yield a product in which a substantial amount of the pyrolyzing resin matrix has been driven off, but there is the additional danger that outgassing may occur at such a rate and in such a manner that the integrity of the refactory fibers or cloth composite may be impaired. In addition where a substantial portion of the resin has been decomposed during the carbonization, a weakened structure may also result.
U.S. Pat. No. 4,185,043 to Shaffer discloses that the properties of polymers may be improved by incorporating therein at least one metal selected from the group consisting of tungsten and molybdenum. The presence of the metal atoms in the basic resin molecule make possible the formulation of resin matrix systems which are capable of absorbing large amounts of energy for specific related applications.